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United States Patent |
5,064,005
|
Krone
|
November 12, 1991
|
Impact hammer and control arrangement therefor
Abstract
Hydraulic hammers are normally controlled by an actuating valve which
controls the flow of fluid from a source of pressurized fluid to the
hydraulic hammer. During certain periods of operation, the actuating valve
totally blocks communication of fluid to the hydraulic hammer, thereby
causing the fluid from the source of pressurized fluid to be expelled
through a relief valve. The subject hydraulic hammer and control
arrangement therefor includes an accumulator for storing the pressurized
fluid from the source of pressurized fluid during periods of fluid
blockage by the actuating valve and for supplementing the flow of fluid
from the source of pressurized fluid when the actuating valve is
communicating pressurized fluid to the hydraulic hammer. This increases
the overall efficiency thereof.
Inventors:
|
Krone; John J. (Dunlap, IL)
|
Assignee:
|
Caterpillar Inc. (Peoria, IL)
|
Appl. No.:
|
516861 |
Filed:
|
April 30, 1990 |
Current U.S. Class: |
173/208; 91/170R; 91/243; 91/300 |
Intern'l Class: |
B25D 009/18 |
Field of Search: |
173/116,134,135
91/243,170 R,300
|
References Cited
U.S. Patent Documents
4034817 | Jul., 1977 | Okada | 173/134.
|
4149602 | Apr., 1979 | James | 173/134.
|
4179983 | Dec., 1977 | Wallace | 173/134.
|
4413687 | Nov., 1983 | Eklof | 173/134.
|
4474248 | Oct., 1984 | Musso | 173/134.
|
4646854 | Mar., 1987 | Arndt et al. | 173/134.
|
4676323 | Jun., 1987 | Henriksson | 173/134.
|
4715265 | Dec., 1987 | Graul et al. | 91/170.
|
4825960 | May., 1989 | Krone | 173/134.
|
4945998 | Aug., 1990 | Yamanaka | 173/134.
|
Foreign Patent Documents |
0168364 | Jan., 1986 | EP.
| |
0236721 | Sep., 1987 | EP.
| |
0352742 | Jan., 1990 | EP.
| |
WO80/01666 | Aug., 1980 | WO.
| |
Primary Examiner: Rosenbaum; Mark
Assistant Examiner: Smith; Scott A.
Attorney, Agent or Firm: Grant; John W.
Claims
I claim:
1. An impact hammer and control arrangement therefor, comprising:
a hydraulic impact hammer having a housing, a piston slidably disposed in
the housing and having a pair of fluid engagement surfaces thereon, a
variable volume gas chamber defined by the housing and one of the fluid
engagement surfaces and filled with a pressurized gas, and a variable
volume hydraulic chamber defined by the housing and the other of the fluid
engagement surfaces;
a source of pressurized fluid;
a supply conduit connected to the source of pressurized fluid;
an actuating valve connected to the variable volume hydraulic chamber and
to the supply conduit and being moveable between a first position at which
pressurized fluid from the source of pressurized fluid is directed into
the hydraulic chamber to retract the piston against the bias of the
pressurized gas in the gas chamber and a second position at which the
hydraulic chamber is vented and fluid flow from the source of pressurized
fluid through the actuating valve is blocked; and
means for storing pressurized fluid from the source of pressurized fluid
when the actuating valve is in the second position and for supplementing
the flow of pressurized fluid from the source of pressurized fluid when
the actuating valve is in the first position said means including an
accumulator connected to the supply conduit, and
is preloaded sufficient to prevent the entrance of fluid thereinto during
the time when the piston is being retracted against the gas charge in the
gas chamber.
2. The hydraulic hammer and control arrangement therefor of claim 1 wherein
the accumulator has a capacity sufficient to store the total output of the
pump during the time that the actuating valve is in the second position.
Description
TECHNICAL FIELD
This invention relates generally to an impact hammer and control
arrangement therefor and more particularly to a control arrangement having
a means for storing pressurized fluid during one sequence of operation and
thereafter using the stored fluid in another sequence of operation.
BACKGROUND ART
Many hydraulic hammers have a hydraulic chamber which receives pressurized
fluid from a hydraulic pump for moving a piston in a direction against a
volume of compressible gas. Once the piston reaches a predetermined
position, an actuating valve is automatically sequenced to a position for
venting the hydraulic chamber, thereby allowing the compressed gas to
rapidly propel the piston in an opposite direction against a cutting tool.
The actuating valve of some of those hammers blocks the flow of fluid from
the pump to the hammer during the propelling stroke of the piston. When
this happens, the pressurized fluid is commonly relieved by a relief valve
connected to the pump output conduit. This reduces the efficiency of the
operation in several ways. First of all, since the pressure relieving
setting of the relief valve must be higher than the normal operating
pressure of the hammer, considerable energy must be expended to pump the
fluid through the relief valve at such high pressure. Secondly, since the
operating speed of the hammer is dependent upon the pump output, a larger
pump is required since some of the pressurized fluid is not being utilized
in the actual operation of the hammer.
One prior art reference relating to this general subject is U.S. Pat. No.
4,715,265, issued Dec. 29, 1987 to Graul et al. That system relates to an
apparatus for vibratory operation of a working piston in which the piston
is moved toward the tool by pressurized hydraulic fluid from a pump
through an actuating valve. The actuating valve has an inlet port
connected to the pump and alternately establishes and blocks communication
of fluid through the valve from the pump to the actuating chamber. A
pressure equalizing storage means or reservoir is also connected to the
inlet port of the actuating valve. However, that reference fails to
provide any functional use for such pressure equalizing storage means.
The present invention is directed to overcoming one or more of the above
problems.
DISCLOSURE OF THE INVENTION
In one aspect of the present invention, an impact hammer and control
arrangement therefor comprises a hydraulic impact hammer having a housing,
a piston slidably disposed in the housing and having a pair of fluid
engagement surfaces thereon, a variable volume gas chamber defined by the
housing and one of the fluid engagement surfaces and filled with a
pressurized gas, and a variable volume hydraulic chamber defined by the
housing and the other of the fluid engagement surfaces. A source of
pressurized fluid has a supply conduit connected thereto. An actuating
valve is connected to the variable volume hydraulic chamber and to the
supply conduit and is moveable between a first position at which
pressurized fluid from the pump is directed into the hydraulic chamber to
retract the piston against the bias of the pressurized gas and a second
position at which the hydraulic chamber is vented and fluid flow through
the actuating valve to the hydraulic chamber is blocked. A means is
provided for storing pressurized fluid from the pump when the valve is in
the second position and for supplementing the output of the pressurized
fluid from the pump when the valve is in the first position.
BRIEF DESCRIPTION OF THE DRAWINGS
The sole figure is a schematic illustration of an embodiment of the present
invention with portions shown in section for illustrative convenience.
BEST MODE FOR CARRYING OUT THE INVENTION
Referring to the drawing, a hydraulic hammer 10 is connected to a control
arrangement 11. The hydraulic hammer 10 includes a housing 12 having a
longitudinally extending stepped bore 13 with the stepped bore 13 having
an enlarged intermediate section 14. A piston 16 is slidably disposed in
the bore 13 and has a flange 17 slidably disposed within the enlarged
intermediate section 14. The piston 16 has an end surface 18 which
functions as a fluid engagement surface and cooperates with the housing 12
to define a variable volume gas chamber 19. The flange 17 has a pair of
angular shoulders 21,22 which function as fluid engagement surfaces and
cooperate with the housing to define a pair of annular variable volume
hydraulic chambers 23,24 respectively at opposite ends of the flange 17.
An impact transfer member 26 is positioned to receive impact blows from
the piston 16 and is suitably connected to a work tool, not shown. The gas
chamber 19 is filled with a pressurized gas in the usual manner.
The control arrangement 11 includes a source of pressurized hydraulic fluid
such as a hydraulic pump 27 connected to a reservoir 28, a control valve
29 connected to the pump 27, and a supply conduit 31. The control valve 29
is moveable between a first position at which the pressurized fluid is
directed from the pump 27 into the supply conduit 31 and a second position
at which the pump 27 and supply conduit 34 are communicated with the
reservoir 28.
An actuating valve 32 includes a body 33 connected to the housing 12 in the
usual manner. The body 33 has a stepped bore 34 with the bore having an
enlarged end section 36. A plurality of annuli 37,38,39 communicate with
and are axially spaced along the stepped bore 39. A valve spool 41 is
slidably positioned in the bore 34 and has a flange 42 disposed in the
enlarged end section 36. The flange 42 has an annular shoulder 43 which
functions as an actuating surface and cooperates with the body 33 to
define an annular actuating chamber 44. The valve spool 41 has a
longitudinally extending axially disposed passage 46 therein and an
annular groove 47 formed on the outer periphery thereof. The body 33 has a
bore 48 opening into the enlarged end section 36 of the bore 43. A plunger
49 is slidably disposed in the bore 48 and abuts the valve spool 41. The
effective area of the annular shoulder 43 is greater than the effective
area of the plunger 49. The body 33 also includes an inlet port 51
connected to the supply conduit 31 and being in communication with the
annulus 38 and the bore 48. An exhaust port 52 connects the enlarged end
section 36 with the reservoir 28. A signal passage 53 is in continuous
communication with the actuating chamber 44 and with the annulus 39.
Depending upon the position of the piston 16, the signal passage is also
in communication with the hydraulic chamber 14, blocked by the flange 17
of the piston 16 or is in communication with the hydraulic chamber 23. A
transverse passage 54 communicates the annulus 37 with the hydraulic
chamber 23 while another transverse passage 56 communicates the hydraulic
chamber 24 with the enlarged end section 36. The valve spool 41 is
moveable between first and second positions. At the first position, the
spool 41 communicates the inlet port 51 with the hydraulic chamber 23,
blocks the inlet port from the annulus 39, and blocks the hydraulic
chamber 23 from the exhaust port 52. At the second position, the hydraulic
chamber 23 is in communication with the exhaust port 52 and the inlet port
51 is in communication with the annulus 39.
A means 57 is provided for storing pressurized fluid from the pump 27 when
the valve spool 41 is in the second position and for supplementing the
output of pressurized fluid from the pump when the valve spool 41 is in
the first position. The means 57 can be, for example, an accumulator 58
connected to the supply conduit 31. A relief valve 59 is also connected to
the supply conduit 31.
INDUSTRIAL APPLICABILITY
The valve spool 41 of the actuating valve 32 is shown in the first position
and the piston 16 is shown in the extended position they would occupy
immediately after the piston 16 has impacted the member 28. Thus, with the
control valve 29 in the position shown, pressurized hydraulic fluid from
the pump 27 is transmitted through the supply conduit 31, the inlet port
51, the annulus 38, the annular groove 47, the annulus 37, and the
transverse passage 54 into the hydraulic chamber 23. The pressurized
hydraulic fluid acting on the annular shoulder 21 retracts the piston 16,
thereby compressing the gas in the chamber 19. As the piston 16 is
retracted, the hydraulic fluid contained in the hydraulic chamber 24 is
exhausted through the transverse passage 56, the enlarged end section 36
and the exhaust port 52 to the reservoir 28. When the piston 16 reaches a
predetermined position at which the annular shoulder 21 clears the signal
passage 53, communication is established between the hydraulic chamber 23
and the signal passage 53. High pressure hydraulic fluid is transmitted
from the hydraulic chamber 23 into the actuating chamber 44 where it acts
against the annular shoulder 43 of the valve spool 41, thereby moving the
valve spool to the second position. With the valve spool in the second
position, the stored energy in the compressed gas in the gas chamber 19
rapidly propels the piston 16 outwardly against the impact member 26. The
fluid in the hydraulic chamber 23 passes through the transverse passage
54, the central passage 46, and the transverse passage 56 to fill the
expanding chamber 24 behind the moving piston. Any excess fluid passes
through the exhaust port 57 to the reservoir 28.
During the outward movement of the piston 16, the flange 17 blocks
communication between the signal passage 53 and the enlarged section 14 of
the bore 13 so that pressurized fluid in the annulus 38 is transmitted
into the actuating chamber 44 to hold the valve spool 41 in the second
position. With the valve spool in the second position, the fluid flow from
the pump 27 to the hydraulic hammer is substantially blocked. However,
under this condition the pressure of the fluid in the supply conduit 31
increases causing the fluid from the pump 27 to enter the accumulator 58
which stores the fluid during the time that the piston 16 is being
propelled outwardly by the gas charge. When the annular shoulder 22 passes
the opening of the signal passage 53, communication is momentarily
established between the actuating chamber 44 and the reservoir 28. The
size of the signal passage 53 is selected to restrict fluid flow
therethrough to create a back pressure in the inlet port 51 and bore 48
sufficient to cause the plunger 49 to move the valve spool 41 to the first
position. When the valve spool reaches the first position, communication
is again established between the inlet port 51 and the actuating chamber
23. Under this condition, the pressurized fluid stored in the accumulator
supplements the flow from the pump 27 to again retract the piston 16 with
the cycle being repeated as long as the control valve 29 remains in the
position shown.
The accumulator 58 is preferably preloaded sufficient to prevent the
entrance of fluid thereinto during the time when the piston 16 is being
retracted against the gas charge in the gas chamber 19. The accumulator
has a capacity sufficient to store the total output of the pump 27 during
the time that the actuating valve spool 41 is in the second position.
In view of the foregoing, it is readily apparent that the structure of the
present invention provides an improved hydraulic hammer and control
arrangement therefor which increases the operating efficiency by storing
pressurized fluid from the pump during periods when the output of the pump
is blocked from the hammer by the actuating valve. Also since the stored
pressurized fluid is then used to supplement the fluid flow from the pump
during the retracting stroke of the piston, a smaller pump can be used to
achieve the same frequency of hammer operation.
Other aspects, objects, and advantages of this invention can be obtained
from a study of the drawing, the disclosure, and the appended claims.
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